Radio-frequency generator



May 29, 1951 D. H. PREIST RADIO-FREQUENCY GENERATOR 2 Sheets-Sheet 2.

Filed Jan. 1'7, 1949 INVENTOR. Oarm/o h. fire/$7 ATTORNEY Patented May 29, 1951 RADIO-FREQUENCY GENERATOR Donald H. Preist, Tiburon, Calif., assignor to Eitel-McCullough, Inc., San Bruno, Califi, a corporation of California Application January 17, 1949, Serial No. 71,290

Claims. 1

My invention relates to generators of radiofrequency power, and more particularly to such a generator capable of delivering large orders of power in the higher frequency ranges, say above 100 mcs./sec., using conventional type negative grid tubes.

In my copending application, Serial No. 42,171, filed August 3, 1948, I have disclosed a new type of R. F. generator embodying an annular cavity resonator operating in conjunction with a plurality of tube units, whereby the power outputs of the individual tube units are combined without appreciable loss.

The object of my present invention is to provide an improved resonator construction for such a multiple unit tube generator.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of my invention. It is to be understood that I do not limit myself to this disclosure of species of my invention as I may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawings:

Figure l is a vertical sectional view of a power amplifier embodying the improvements of my invention; and

Figure 2 is a plan View of the same.

In terms of broad inclusion, the radio-frequency generator of my invention comprises a plurality of electron tube units disposed in a circle about an axis, and a pair of annular cavity resonators coaxial with the circle and having conductors connected to electrodes of the tube units, each resonator comprising two communicating annular cavity sections. As embodied in an amplifier one of these cavity resonators functions as the input circuit and the other as the output circuit, means being provided for feeding power to the input resonator and for delivering power from the output resonator, and means being provided in the resonators for tuning them to the resonant frequency. In the resonator construction of my present invention, the cavity sections of both the input and output resonators extend in the same direction relative to a plane defined by the circle of tube units. In other words, the cavity sections of the output resonator are folded back to lie alongside the cavity sections of the input resonator. By this arrangement, the amplifier can be designed so that the tube units are exposed externally rather than being confined by the cavity structure. This construction not only. makes it more convenient 'to service the 2 equipment and replace the tubes, but also provides a very compact generator structure.

In greater detail, and referring to the drawings, my improved R. F. generator constructed as an amplifier comprises a plurality of electron tube units l disposed in a circle about a common axis, which tube units are of like structure and have like characteristics. While four tube units are shown, it is understood that any desired number may be employed, depending upon the power output required. Any conventional type of negative grid electron tube may be used for the units I, the triode type of tube illustrated having a cathode 2, grid 3 and anode 4, the anode being external and all the electrodes being preferably cylindrical and coaxial.

The tube units employed also preferably have coaxial terminals for the electrodes, such as the cathode terminal 6 opposite the anode and the grid terminal ring I interposed in the glass envelope wall between the cathode terminal and anode. The heating structure for the cathode is not shown but may comprise any suitable means such as an inner filament for heating the cathode cylinder 2 by electron bombardment, in which case the filament leads preferably extend out through the tubular cathode terminal 6.

The amplifier has a pair of annular cavity resonators common to the tube units l, functioning as the input and output resonant circuits for such units. Each resonator has two communicating annular cavity sections arranged coaxially with the circle of tube units, thus the input resonator has the two annular cavity sections 8 and 9 communicating through spaces between the lower portions of the tube units, and the output resonator has the two annular cavity sections I l and I2 communicating through spaces between the upper portions of the tube units. This symmetrical arrangement of the cavity resonators with respect to the tube units is an important feature in my R. F. generator.

The two cavity sections 8 and 9 of the input resonator extend downwardly from a plane defined by the circle of tube units, say a plane passing through the mid-portions of the units l. Cavity sections H and I2 of the output resonator also extend downwardly from such plane and surround the input resonator.

In my earlier application, hereinbefore mentioned, both cavity sections of the output resonator extend upwardly, which is entirely satisfactory electrically but results in a rather lengthy overall structure and makes it hard to get at the tubes. By folding down the cavity sections of the output resonator, as shown in Figure 1, it will be seen that the tube units are exposed on the top deck of the amplifier, which is a more convenient and desirable arrangement from the mechanical standpoint.

The several cavity sections of the resonators are defined by metallic boundary walls or conductors which make up the physical structure of the amplifier. As illustrated, the annular cavity sections of the resonators are defined by six concentric Wall conductors I3, I4, I6, I'I, I8 and I9; the conductors I3 and I4 beingthesh ortest, the conductors I6 and I! being'oi intermediate length, and the conductors I8 and I9 being the longest. The shorter walls are connected across the top by a metal ring 23, these parts comprising an inner conductor of the input resonator. This inner conductor is connected tethe cathode 2 of each of the tube units, preferablya dividing wall between the input and output resonators. vIt is connected to the grid 3 of each of the tube units, preferably by having the grid terminal rings I seated in apertures or sockets spaced about the ring 2!. Cavity sections 8 and 9 of the input resonator are thus connected about their circumference by the communicating space formed between the transverse wall members and 2I.

Wall conductors I8 and I 9 are joined across.

the top by a transverse wall conductor 24 which is connected to the anode 4 of each of the tube units. Cavity sections II and I2 of the output resonator are thus also connected about their circumference by the communicating space formed between the transverse wall members 2I. and 24.

By this arrangement it will be seen that the cavity resonators are coaxial with the circle of tube units, and are disposed in such a manner that the tube units are located between the annular cavity sections of the resonators, with the cathodes connected to a conductor of the input resonator, the anodes connected to a conductor of the output resonator and the grids connected to a common transverse conductor between the resonators. This symmetrical arrangement of the cavity resonators with respect to the tube units is an important feature as pointed out in my earlier application hereinbefore mentioned.

It will also be noted that the folding down of the cavity sections II and I2 of the output resonator in my present construction places the tube units I on an open deck whiph is a desirable feature from the standpoint of tube replacement and servicin the equipment. Connection of the anodes 4 to the transverse deck plate'or conductor 24 is preferably made by terminal rings 26 on the anodes of a size to seat down on the deck 24. Coolers 27 on the anodes are placed above the anode terminal rings 23. These coolers may be of the finned type for-forced air cooling as illustrated, or may be suitable jackets for water cooling the anodes. In either case, the coolers are exposed for convenient connection ofairor 4 R water ducts. The apertures in the transverse conductors 24, 2I and 20 are of a size to permit withdrawal and replacement of the tube units.

The several cylindrical conductors of the resonators are held mechanically in position by rings 28, 29, 30 and 3| of suitable insulating material located between the conductors at the bottom of the generator. Any suitable metal such as brass may be used for the various cylindrical and transverse conductors described.

' Adjustable means are provided for tuning the input and output resonators to the desired resonant frequency. For this purpose a pair of movable annular metal rings or plungers 32 and 33 are'provided in the input resonator, forming end -walls in the cavity sections 8 and 9 respectively.

' ner wall conductors I3 and I4, and axial adjustment is achieved by means of plunger rods 34 and 35 of insulating material projecting out through the supports 29 and 30. These rods may be connected externally to insure that the plungers are adjusted in unison. Plungers 32 and 3,3 are preferably spaced from the wall conductors I6 and I! and have cylindrical flanges 36 and 31 so that the devices also function at chokes to confine the R. F. and isolate D. C. voltages. For this purpose the flanges 36 and 31 are made effectively a quarter-wave long at the operating frequency, telescoping sleeves (not shown) being preferably provided on the flanges to adjust their length.

In a like manner plungers 38 and 39 are provided in the cavity sections I I and I2 of the output resonator, which plungers are slideably mounted on the wall conductors I8 and I9 respectively and have flanges spaced from the walls I6 and IT. These plungers thus serve as means for tuning the output resonator and as chokes for confining the R. F. and isolating the D. C. voltage, tuning adjustment being effected by the rods 4| and 42.

The D. C. voltages may be applied to the tube electrodes in any suitable manner. In the amplifier illustrated, which is essentially a grid-separation type of circuit, the positive D. C. anode potential is applied by connection to the outer conducting wall as indicated at 43, and the grid bias voltage is applied via the conductor II--2l by a grid bias resistor as indicated at 44. Suitable leads (not shown) for the cathode heaters for the several tube units are conveniently brought out through the hollow space between the conductors l3 and I4.

Instead of using the tuning plungers as chokes, the D. C. voltages may be isolated by suitable bypass condensers at the anode and grid terminals of the tube units, as will be appreciated by those skilled in the art, in which case the tuning plungers 32, 33, 38 and 39 may be simple shorting bars slideable along the conductor walls. This also has the advantage of removing the D. C. anode voltage-from the Wall conductors of the generator, the anode voltage connections being made directly to the anodes of the tubes. Of course the electrodes are still connected for R. F. to the conductors of the resonators, it being understood that such connections may be established' through suitable bypass condensers as well as by direct connection.

Any suitable means may be employed for transferring and coupling R. F. power into and out of the resonators. For example, a coaxial transmission line 46 cooperating with a probe 41 suitably located in input cavity may be used for trans:

ferring driving power from a suitable source of drive to the input resonator. In a like manner R. F. power may be transferred from the output resonator to the load by a coaxial transmission line 48 and associated probe 49 located in the output cavity.

It is understood that the generator may be operated as a self-excited oscillator by eliminating the input transmission line 46 and by providing suitable feedback. coupling means for establishing feedback of energy from the output resonator to the input resonator to sustain oscillation.

In my improved R. F. generator, operating either as an amplifier or as an oscillator, the overall diameter of the generator may be increased indefinitely to accommodate an indefinite number of tube units, depending upon the amount of power required. Furthermore, the multiple unit tube generator described will operate well in the higher frequency ranges, say above 500 mcs./sec., without loss of efficiency compared to that obtainable from a single tube unit. The total power output from n tube units, as measured at the load, is substantially n times that obtainable from a single tube unit in an efficient single unit tube generator.

While I have described my generator in connection with triode units, it is understood that tube units having additional electrodes such as tetrodes may be employed, in which case additional annular, coaxial and symmetrical circuit members are employed.

I claim:

1. A radio-frequency generator comprising a plurality of electron tube units disposed in a circle about an axis and each having electrodes, a cavity resonator common to the tube units and having two communicating annular cavity sections, the resonator being coaxial with said circle and having a conductor connected to an electrode of each of said tube units, and a second cavity resonator common to the tube units and having two communicating annular sections, the second resonator being coaxial with said circle and having a conductor connected to another electrode of each of said tube units, the cavity sections of both of said resonators extending in the same direction relative to the plane of said circle,

2. A radio-frequency generator comprising a plurality of electron tube units disposed in a circle about an axis and each having electrodes including an anode and cathode, an output cavity resonator common to the tube units and having two communicating annular cavity sections, the output resonator being coaxial with said circle and having a conductor connected to the anode of each of said tube units, and an input cavity resonator common to the tube units and having two communicating annular sections, the input resonator being coaxial with said circle and having a conductor connected to the cathode of each of said tube units, the cavity sections of both of said resonators extending in the same direction relative to the plane of said circle.

3. A radio-frequency generator comprisin a plurality of electron tube units disposed in a circle about an axis and each havin electrodes including an anode and cathode and grid, an output cavity resonator common to the tube units and having two communicating annular cavity sections, the output resonator being coaxial with said circle and having a conductor connected to the anode of each of said tube units, an input cavity resonator common to the tube units and having two communicating annular sections, the input resonator being coaxial with said circle and having a conductor connected to the cathode of each of said tube units, the cavity sections of both of said resonators extending in the same direction relative to the plane of said circle, and a conductive member common to said resonators extending transversely of said axis and connected to the grid of each of said tube units.

4. A radio-frequency generator comprising a plurality of electron tube units disposed in a circle about an axis and each having electrodes including an anode and cathode, an output cavity resonator common to the tube units and having two communicatin annular cavity sections, the output resonator being coaxial with said circle and having a conductor connected to the anode of each of said tube units, and an input cavity resonator common to the tube units and having two communicating annular sections, the input resonator being coaxial with said circle and having a conductor connected to the cathode of each of said tube units, the cavity sections of both of said resonators extending in the same direction relative to the plane of said circle, and the cavity sections of said input resonator being disposed intermediate the two cavity sections of the output resonator.

5. A radio-frequency generator comprising a plurality of electron tube units disposed in a circle about an axis and each having electrodes including an anode and cathode and grid, an output cavity resonator common to the tube units and having two communicating annular cavity sections, the output resonator being coaxial with said circle and havin a conductor connected to the anode of each of said tube units, an input cavity resonator common to the tube units and having two communicatin annular sections, the input resonator being coaxial with said circle and having a conductor connected to the cathode of each of said tube units, the cavity sections of both of said resonators extending in the same direction relative to the plane of said circle, and a conductive member common to said resonators extending transversely of said axis and connected to the grid of each of said tube units, said conductors each comprising an annular plate transverse to the said axis, said plates being spaced axially and defining therebetween radial passages afiording communication between the two sections of each resonator.

DONALD H. PREIST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,284,405 McArthur May 26, 1942 2,363,641 Carlson Nov. 28, 1944 

